I have an irregular convex octagon, alternating between 4 large edges, say 'a' mm long and 4 small edges, say 'b' mm long, is there a formula available so that I can work out the minimum size sit a circle with a radius of 34.25mm inside it thank you

James,

What you can do is somewhat limited by the theorem of Euclid that tells you that the tangents to a circle from an outside point must have the same length. All you can do is place your circle inside a square (with the diameter of the circle equal to the length of a side of the square), then cut the four corners off the square — the shorter sides of the resulting octagon will not touch the circle.

Chris

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